Date
11 Aug 2014
Cultivation of the wild indigenous fruit tree, Dobera glabra, could help to achieve greater food security in dry regions of Ethiopia.
Dobera glabra has great potential as an agroforestry species in dry areas due to its ability to adapt to drought and naturally saline soils, and provide a food source during ‘hungry’ times, concludes a study published in the Open Journal of Forestry.
The study is the first to analyse the drought and salinity tolerance of Dobera glabra and several other species in the savannah woodlands of Ethiopia. Scientists investigated the water potential and osmotic potential of 9 different tree species in the semi-arid Awash National Park, about 200km from the capital, Addis Ababa; an area prone to drought and salinity and known for high food insecurity.
Lead author of the study, Dr Aster Gebrekirstos, a scientist with the World Agroforestry Centre, explains how water potential and osmotic potential are indicators of drought and salinity stress.
“Dobera glabra had both the lowest water potential and osmotic potential of all the species we studied, explaining its ability to to flourish in drought years and its wide distribution in extremely dry and saline areas,” explains Gebrekirstos.“These qualities give it an advantage over other plants and allow it to thrive in drought and salinity prone areas.”
According to Gebrekirstos, the species shows great promise for use in the regeneration of degraded land. In the study area around Awash River, many farms have been abandoned due to salinity caused by inappropriate irrigation practices, soil leaching, overgrazing and fire. Large areas of degraded farmland in this area have been invaded by exotic weeds that thrive on saline soils.
“A plant like Dobera glabra, with its capacity to regulate water use in response to water depletion and high salinization, can survive and be productive in environments such as this,” says Gebrekirstos. “It could be an important part of the solution to rehabilitating farmland in this area, and other areas with similar conditions.”
The study also notes the species’ potential in areas where climate change – such as increased temperature and decreased water availability – is likely to exacerbate soil salinity.
But the potential of Dobera glabra (or Garssa as it called by the Afar people) isn’t just limited to revegetation and land reclamation efforts. The tree also has many qualities that make it appealing for agroforestry and local knowledge may help in climate change adaptation.
“Economically, socially and environmentally, Dobera glabra is a very valuable tree,” says Gebrekirstos. One of its many attributes is that its fruit ripens during the drought period, providing food when food is scarce. The tree’s timber is used in heavy construction, for agricultural implements, fuelwood, watering troughs and other domestic items. The leaves can be used as fodder for livestock, and its roots and leaves are used for traditional medicines. In many villages the tree is also planted to provide shade.
“By domesticating Dobera glabra for on-farm cultivation, we can go a long way towards tackling food insecurity in southern and north eastern Ethiopia and similar environments.”
When rains are delayed or fail Dobera glabra does the opposite to most trees and produces new shoots, fruits and seeds. Because of this abundant blooming, many farmers and pastoralists in the south and north-east of the country use the tree as an indicator of drought and potential food scarcity or famine.
“This local knowledge shows us how farmers use their surroundings as early warning system to adapt to climate variability and change.” Although farmers have no explanation as to why Dobera glabra behaves the way it does, Gebrekirstos says the study sheds light on why the tree has a comparative advantage over other co-occurring species; linking local knowledge with tree physiology.
Drought and soil salinity are the main factors that limit plant growth. In environments prone to drought and salinity, such as occur across Ethiopia, it is common to find plants that have adapted to the harsh conditions. Gebrekirstos believes that understanding the characteristics of such plants will help to assess the suitability of species for revegetation, domestication and reclamation efforts in specific environments.
In their study, Gebrekirstos and fellow scientists found a wide range of responses to water and osmotic stress among the 9 different species, demonstrating that each employs different strategies to offset the deleterious effects of drought and osmotic stress and adapt to the conditions.
“Different species have niche preferences which affect their distribution and tolerance range in case of climate change-induced drought and changes in site conditions.”
The authors recommend further investigation into the detailed processes involved in the adaptation of species to saline soils, such as whether it involves the regulation of uptake and/or compartmentalization of salt and how this impacts on growth and productivity.
Download the full study:
Gebrekirstos A, Teketay D, Mitlöhner R (2014). Responses of Dobera glabra and Eight Co-Occurring Species to Drought and Salinity Stress at a Savanna-Scrub Ecotone: Implications in the Face of Climate Change. Open Journal of Forestry 4, pp 327-337.